Ceramics-Silikáty 43, (1) 12 - 17 (1999)

Boehmite derived alumina gels (grains and sticks) containing Fe₂O₃ in the range of 1 to 6 wt. % were sintered at 1350 °C for 3 hours. Relative density, strength and unexpectedly also the size of α-Al₂O₃ crystals increase with Fe₂O₃ content. A bimodal microstructure of anisotropic α-Al₂O₃ crystals is observed at and above 3 wt.% content of Fe₂O₃. Anisotropic growth of α-Al₂O₃ crystals is attributed to the presence of Fe²⁺ and to the specific nucleation effect of α-Fe₂O₃. Due to high strength and the relatively small size of α-Al₂O₃ crystals a Fe₂O₃ content of 3 wt.% seems most appropriate when applications of the material as abrasive grains are intended.